Sheet advancing drive for printing presses



Jan. 7, 19.64 R. GUNTHER 1 3,116,923

SHEET ADVANCING DRIVE FOR PRINTING PRESSES Filed Aug. 7, 1961 INvE/vTORI ROIHNCL Gumch 12w azs mw g United States Patent 1 3,116,923 SHEETADVANClNG DRIVE FOR PTlNG PRESSES Roland Gunther, Haunstetten, nearAugsburg, Germany, assignor to Maschinenfabrik Augsburg-Nurnberg A.G.,Augsburg, Germmy Filed Aug. 7, 1961, Ser. No. 129,702 Claims priority,application Germany Sept. 9, 1960 3 Claims. (Cl. 271-51) This inventionrelates to the driving means for a sheet transfer or advancing drive fora printing press. In this kind of a drive, the swing gripper for thesheet advancing is turned by two eccentrically moving rocker armsmounted on the same side of the press, which rocker arms are constantlyurged against the drive cams by a spring in order to eliminate the playin the drive mechanism.

In a sheet printing press, it is conventional to transfer the blanksheet from the stacking table of the press by means of a forward andback grasping device onto a cylinder moving at an equal speed or onto adrum lying in front of a cylinder. The sheet of paper lying at rest onthe stack must be accelerated as quickly as possible to the velocity ofthe circumferential surface of the cylinder and also must be offered tothe gripping device on the cylinder in a position which is always thesame with regard to the cylinder. In order to obtain the proper registerin the printing of several colors, one on top of the other, by runningeach sheet through the press several times, the delivery or transfer ofthe sheet from the grasping device to the cylinder must take placealways in exactly the same position and even when the speed of theprinting press is changed.

Since modern printing presses ordinarily have a high printing speed andbecause of the use of printing cylinders as small as possible indiameter in order to save expense, only a very small percentageof thetime for one revolution of the cylinder is available for coaction withthe sheet transfer device which results in that large forces due to thehigh accelerations and stoppings of the transfer device prevail.

Sheet transfer devices are well known in which gear trains, planetarygears or a reciprocating arm slidable in a slot are used for obtainingthe forward and back movement.

On the other hand, the forward movement of the transfer device has beenobtained by means of only one rocker arm which is moved eccentrically ona cam surface, and is joined to the transfer device either by means of agear train or a pull rod. Tension springs are used to obtain the returnor back movement and also to hold the rocker arm against the camsurface. Such springs are connected at one end to the press frame and atthe other end either to the swing gripper shaft or the rocker arms.Alternatively, instead of joining the spring to the press frame, asecond rocker arm is employed which follows another cam curve lying onthe same side as the first cam curve in such a way that the strength ofthe spring between the two arms has a tension which is uniform or adaptsitself to the forces arising during the operation of the drivemechanism. However, the shaft of the swing gripper in this case isactuated by means of a single pull rod joined to one of the rocker armsso that any play between the two joints of the pull rod is not balancedout.

The existence of such play or movement by reason of the forces arisingduring the operation of the transfer device is very disadvantageous inthat, when the printing press speed is changed, a corresponding changeoccurs in the relative position of the sheet transfer device. Attemptshave been made to correct this fault by using socalled register teethwhich force a synchronization between the transfer device and thecylinder at the moment the sheet is transferred. However, such teethmust be very carefully fitted and are subject to constant wear and tearwhich means a frequent replacement of the same.

Pull pressure or torsion springs have been installed between the swinggripper shaft and the press frame in an effort to control the playbetween the joints of the pull rod. Because of the great angle of turnof the swing gripper shaft for the transfer, very high spring forcesoccur at the upper dead point of the shaft which forces produce a highback-pressure between the rocker arm and the cam. Such backpressuredisturbs the uniform running of the whole press since the rocker armfollows the curve of the cam and produces the effect that the drumpreceding the printing cylinder is trying to cooperate with a forcewhich in each revolution of the cylinder is directed first in one andthen in the opposite direction. The fluctuations in the velocity ofrevolutions of the cylinder or the drum must be absorbed by the flywheel mass of the cylinder or by the rotational forces on the othermoving parts of the press. In small printing presses having thereforesmaller rotating masses, an oscillation of the whole press takes placewhich produces serious difficulties in printing techniques.

Another known guiding mechanism for the sheet tnans fer device attemptsto eliminate play by connecting the rocker arms with each other by meansof a spring, the rocker arms being joined to the swing gripper shaft foractuating the same. In this case, the drive cams and rocker arms aremounted on opposite sides of the press and since teeth segments are usedto actuate the pull rod joined to the transfer device, such constructionis not suitable for large presses because of lack of installation space.Moreover, a rack and pinion drive is subject to considerable wear andtear which influences the proper register for the sheets.

A drive mechanism in which the swing gripper shaft for the sheettransfer which is actuated by two eccentrically moving rocker armsarranged on the same side of the press frame and having the rocker armsconsistently spring-pressed against the cams, the aforesaiddisadvantages are [avoided according to this invention and a drivemechanism free of play achieved by actuating the swing gripper shaft bymeans of two pull rods connected to the rocker arms with one of the pullrods having a spring installed therein so that the two pull rods workagainst each other. By this means, the swing gripper shaft follows,during its backward movement, the movement which is given by one cam, orthe counteracting cam, so that the movement is free of any play in thejoints by reason of the spring pressure. This structure is inexpensiveand space saving. In addition, this invention uses simple parts whichare capable of resisting wear and tear and need little maintenance sothat the value and use of the press is raised substantially.

The pull rods are preferably connected to the two opposite ends of thedouble arm lever secured to the swing gripper shaft for the transfer.Since the spring pressure is adjusted so that it is greater than anyforce produced during one complete rotation of the transfer device, theplay possible in the various joints at any position of the drivingmechanism does not have any effect since the joint pins are alwaysplaced against the same spot in the wall of the bearing by the springpressure. Off-register of the sheet due to change in press speeds isavoided without using an additional spring force on the sheet transfermechanism itself which would have to be increased with each forward orbackward movement to many times the created force in older mechanisms.Only the accelerating and retarding forces which occur in the reversemovement of the transfer device and the swing gripper shaft have anyeifect on the cams and these forces are alternately absorbed by the twocams as pressure forces from the rocker arms. By correctly choosing thereversing point of the rocker arms, the circumferential component of thepressure force that arises according to the corresponding position ofthe angle of the cam can be relatively small. The turning moment that iscreated in the cams by the circumferential component is alternatelyapplied to the two cams, and because of the two parallel rocker arms, ithas an effect always toward the direction of rotation of the cams sothat an almost uniform holding effect is achieved which forces thedriving gears for the cams into a constant contact position with thedriving teeth surfaces. 1

As the spring pressure is adjustable, a pro-stressing within the drivingbars can be given so that the forces are exceeded but slightly and thattherefore no needlessly high bearing pressure is produced in the joints,Due to the arrangement of the spring on the return stroke side of theswing gripper and an adjustable stop, the spring is locked more stronglyin the stop position and the swing gripper is pressed heavily againstthe steps which eliminates any vibration when transferring the sheet.

The means by which the objects of the invention are obtained aredescribed more fully with reference to the accompanying schematicdrawings, in which:

FIGURE 1 is a side elevational view of the drive for the sheet transferdevice;

FIGURE 2 is a schematic View FIGURE 1;

FIGURE 3 is a view of a modification of FIGURE 2.

As shown in FIGURES 1 and 2, a cam 1 and a counteracting cam 2 aredriven in the same direction from the press cylinder or the preliminarydrum and each cam actuates, respectively, its rocker arm 3 and 4. Theforward movement of the transfer device is given by cam 1 actuatingrocker arm 3. Arm 3 is connected to a rigid pull rod 5 which, in turn,is joined to the free end of the double arm lever 6 fastened to theswing gripper shaft 7. The opposite end of lever 6 is joined to a pullrod 8 which, in turn, is connected to rocker arm 4. Pull rod 8 slidesthrough a slotted guide 11 secured to the end of double arm lever 6 sothat spring 10 is under compression between the guide 11 and theadjustable abutment 12 secured to the outer end of rod 8. Thismodification has the advantage in that, if spring 19 should break, nodamage is done to the rest of the drive mechanlsm.

In the modification of FIGURE 3,. the compression spring 10 of FIGURES 1and 2 is replaced by a tension of the drive shown in 4 spring 9, whichforms a part of pull rod 8 and thus this invention produces a powerconnected transmission. The effect is the same as that obtained inFIGURES 1 and 2.

An adjustable stop 13 is mounted adjacent swing gripper shaft 7 so as tolimit the movement of the arm 7a secured to shaft 7. Consequently, atthe end of the reverse stroke of the transfer device, an additionaltensioning or compressing of the springs 9 and 1t) respectively isobtained.

Having now described the means by which the objects of the invention areobtained,

I claim:

1. In a printing press, a drive for a sheet advancing device comprisingtwo drive cams, two rocker arms engaging said cams, respectively, aswing gripper shaft, a double arm lever fastened to said gripper shaftfor turning said shaft alternately in opposite directions, a first pullrod connecting one of said rocker arms to one end of said double armlever, a second pull rod joined to the other of said rocker arms andslidably engaging the other end of said double arm lever, and a springinterconnecting said second pull rod and said other end of said doublearm lever for spring linking the pull rods together through said doublearm lever to prevent play in the drive for said swing gripper shaft.

2. In a printing press as in claim 1, said second pull rod and saidspring being on the reverse movement side of said gripper shaft.

3. In a printing press as in claim 2, further comprising stop means forlimiting the extent of the reverse movement of said gripper shaft andfor strengthening the force of said spring means.

References Cited in the file of this patent UNITED STATES PATENTS394,585 Lester Dec. 18, 1888 585,105 Keeley et a1. June 22, 1897 978,783Rose Dec. 13, 1910 986,634 Jackson Mar. 14, 1911 1,335,876 Coupe Apr. 6,1920 2,143,049 Belluche Jan. 10, 1939 2,184,785 Upham Dec. 26, 19392,635,875 \Verner Apr. 21, 1953 2,649,863 Francis et a1 Aug. 25, 19533,001,416 Kalbermatten Sept. 26, 1961 FOREIGN PATENTS 22,277 Norway Apr.25, 1911

1. IN A PRINTING PRESS, A DRIVE FOR A SHEET ADVANCING DEVICE COMPRISINGTWO DRIVE CAMS, TWO ROCKER ARMS ENGAGING SAID CAMS, RESPECTIVELY, ASWING GRIPPER SHAFT, A DOUBLE ARM LEVER, FASTENED TO SAID GRIPPER SHAFTFOR TURNING SAID SHAFT ALTERNATELY IN OPPOSITE DIRECTIONS, A FIRST PULLROD CONNECTING ONE OF SAID ROCKER ARMS TO ONE END OF SAID DOUBLE ARMLEVER, A SECOND PULL ROD JOINED TO THE OTHER OF SAID ROCKER ARMS ANDSLIDABLY ENGAGING THE OTHER END OF SAID DOUBLE ARM LEVER, AND A SPRINGINTERCONNECTING SAID SECOND PULL ROD AND SAID OTHER END OF SAID DOUBLEARM LEVER FOR SPRING LINKING THE PULL RODS TOGETHER THROUGH SAID DOUBLEARM LEVER TO PREVENT PLAY IN THE DRIVE FOR SAID SWING GRIPPER SHAFT.